Optically active compounds are useful as starting materials or as intermediates for making drug compounds, pesticides, herbicides, and the like. For example, optically active phenylalanine may be used to make 2-amino-4-phenylbutanoate derivatives, such as enalapril. See H. Urbach & R. Henning, Tetrahedron Letters, Vol. 25, p. 1143 (1984).
WO 2009/111700 describes various oxadiazoanthracene derivatives which are active as modulators of the human GLP-1 receptor. When such compounds are substituted at the 3-position of the oxadiazoanthracene ring system, a stereocenter results. In many instances, the substituent at the 3-position is a substituted benzyloxyphenyl moiety. In synthesizing these molecules, it is desirable to employ intermediates that are stereoisomerically enriched in the desired epimer. Thereby one may improve the yield of the resulting stereoisomer, which reduces material use and waste.
WO 2008/051563 discloses optically active mandelic acid derivatives and methods of making such compounds. Such compounds (or derivatives thereof) may be used to synthesize stereoisomerically enriched (or even stereoisomerically pure) mandelic acid derivatives that may be used to synthesize many of the oxadiazoanthracene derivatives described in the above publication. WO 2008/051563 describes a synthetic method that employs an enzyme, particularly a lipase. While such enzyme-mediated syntheses may be useful in many contexts, it may also be useful to employ other means to make stereoisomerically enriched optically active mandelic acid derivatives. For example, in larger-scale syntheses, it may be useful to make stereoisomerically enriched optically active mandelic acid derivatives without having to employ an enzyme.
Therefore, there is a continuing need for new chemical intermediates and synthetic methods employing such intermediates, where such compounds and methods may be useful for making stereoisomerically enriched optically active mandelic acid derivatives.